Influence of operating parameters on photocatalytic degradation of phenol in UV/TiO2 process

The use of hydrogen peroxide (H 2 O 2 ) for improved photocatalytic degradation of phenol in aqueous suspension of commercial TiO 2 powders (Degussa P-25) was investigated. Photodegradation was compared using direct photolysis (UV alone), H 2 O 2 /UV, TiO 2 /UV, and H 2 O 2 /TiO 2 /UV processes in a batch reactor with high-pressure mercury lamp irradiation. The effects of operating parameters such as catalyst dosage, light intensity, pH of the solution, the initial phenol, and H 2 O 2 concentrations on photodegradation process were examined. It was shown that photodegradation using H 2 O 2 /TiO 2 /UV process was much more effective than using either H 2 O 2 /UV or TiO 2 /UV process. The effect of the initial phenol concentration on TOC removal was also studied, demonstrating that more than 8 h was required to completely mineralize phenol into water and carbon dioxide. For all the four oxidation processes studied, photodegradation followed the first-order kinetics. The apparent rate constants with 400-W UV ranged from 5.0 × 10 −4 min −1 by direct photolysis to 1.4 × 10 −2 min −1 using H 2 O 2 /TiO 2 /UV process. The role of H 2 O 2 on such enhanced photodegradation of phenol in aqueous solution was finally discussed.